Impact tool



Nov. 20, 1951 w. G. MrrcHl-:LL 2,575,523

IMPACT TOOL Filed Feb. 16, 1946 2 SHEETS--Sl-IEET 1 'amv/ 25 Afro/FNM Nov. 20, 1951 w. G. M|TcHELL 2,575,523

IMPACT TOOL Filed Feb. 15, 1946 2 SHEETS-SHEET 2 Patented Nav. 2o, 1951 IMPACT TOOL Walter G. Mitchell, Aurora, Ill., assignor to Independent Pneumatic Tool Company, Chicago,

Ill., a corporation of Delaware Application February 18, 1946, Serial No.'648,063v

(Cl. Mib-30.5)

1 Claim.

This invention relates to improvements in portable power operated impact wrenches and like tools for screwing up and unscrewing nuts and bolts by power.

The invention. while relating to tools of the character referred to, is particularly concerned with the impact clutch mechanism employed in such tools for delivering a series or succession of rotational hammer blows on the anvil jaws of the clutch to tighten the nut -or bolt being set or to loosen a tight nut or bolt .being removed, the invention having among its principle objects the following;

To provide means for controlling the impact action of the clutch to selected jaws of the anvil member whereby a longer period of free rotative movement is afforded the hammer member to accelerate suiciently to deliver more powerful hammer blows on the vanvil jaws with a lighter driving or tool motor;

To accomplish said control action through the anvil member of the clutch;

To accomplish said control action through the openings provided in the anvil member for the clutch elements on the hammer member to move into and ou t of the path of the jaws on said anvil member;

To accomplish said control action by having said openings receive only predetermined clutch elements in the rotative operation of the hammer member;

To have said openings offset axially of the anvil member to receive a registering clutch element only and not a non-registering one in each rotative cycle of the hammer member;

To have said offset openings provide trackways therebetween to prevent the clutch elements from entering the openings to clutch and strike the jaws with respect to the openings with which the clutch elements do not register;

To have said openings substantially equal in size and shape and the clutch elements with impact delivering portions corresponding in width and arrangement to the openings in respect to which each clutch element is respectively adapted to pass; and

To provide the improved clutch construction hereinafter described and claimed.

In the accompanying drawings- Fig. 1 is a longitudinal sectional view with parts in elevation of a tool embodying my improved impact clutch, the section being taken on line I-I of Fig. 2;

Fig. 2 is a cross-sectional view taken on line 2--2 of Fig. 1 showing the clutch elements of the clutch in driving engagement with the anvil jaws;

Fig. 3 is a sectional view of the clutch similar to that shown in Fig. l, the clutch elements being shown held in their retracted or declutched positions by the control means hereinafter described; Fig. 4 is a cross-sectional view taken on line 4 4 of Fig. 3;

Fig. 5 is a side elevational view of the anvil menber of the clutch removed from the tool; an

Fig. 6 illustrates the cam action of the clutch.

In the accompanying drawings, I have shown the impact clutch of my invention applied to a portable hand held, hand manipulated power tool of the pneumatlcally operated type. The outside motor case I of the tool is provided with a side handle 2 which containsv a supply passage (not shown) for furnishingcompressed air for operating vthe tool motorlocated within said motor case. 'I'he throttle valve (not shown) for the tool is mounted inthe handle 2 and is opened by a spring biased trigger block I slidthe rotary type having a rotor l equipped with radial blades 5 slidably mounted in slots .6 in

the rotor and working in conjunction with a cylinder 1 doweled or otherwise fixed against rotation in the motor case'as shown. 'I'he cylinder 1 is clamped in the motor case between end plates, only the lower one 8 being shown in Fig. 1, and said lower end plate mounts the bearing unit 9 for the lower trunnion or shaft section I0 of the rotor l. A reversing valve II, shown in Fig.'1, controls the direction of rotation given to the tool motor, there being a suitable porting system in the tool construction for this purpose. The reversing valve II has a handle I2 whereby the operator handling the tool may set the valve for either a clockwise or a counterclockwise rotation for screwing up or unscrewing nuts or bolts as may be required.

The impact clutch mechanism of my invention is located at the forward end of the tool within a housing section I3 in the form of a casting bolted or otherwise flxedly secured to the motor case I as will'be apparent from Fig. l. The for- `ward or outer end of the case Il is provided with a bushing I4 which provides a bearing for the spindle portion I5 on the driven or anvil member I6 of the clutch device. 'I'he spindle I6 is fashioned to receive and drive a nutor bolt ing the .iaw or anvil members 2|, 2| therebetween. These jaw members 2| extend axially of the anvil member I6 and the latter has an outside diameter to locate the jaws relatively close to the inner surface of the casing section |2 when the partsare in assembled relation as shown in Figs. l and 3. The opposite sides 22. 22 of the jaws receive the impact blows of the clutch in its reverse rotation.

Located within the anvil member I6 isa carrier member 2l comprising upper and lower plates 2l, 2l connected for rotation in unison by an interpod shaft 21. 'I'he upper plate 25 is located within the upper end of the anvil member I2 and is integrally connected with vor splined to the shaft 21. The lower plate 26, also within the anvil member l2 at its lower end, fits on a noncircular section 21a of the shaft 21 as shown in Figs. l and 3. Ihe lower end portion of the shaft 21 extends into and is journalled in the spindle I2 which is hollow as shown. A spacer plate 22 is interposed between the lower plate 22 and the anvil wall I2 as shown. The upper` plate 25 has a non-circular socket 22 to receive the like shaped end of the rotor trunnion Ill to provide adirection connection between them.

A revoluble hammer member 2 2 in solid form. except for its diametric cross-slot 2|, is rotatably mounted on the carrier shaft 21 between the plates 2l, 22. The hammer member 2li conforms substantially to the inside diameter of the anvil member I2 and has suflicient mass or weight to deliver powerful hammer blows in the striking or impact action of the clutch.

These blows are generated by impact elements or dogs 22, 22a slidably mounted in the hammer member slot 2|. The latter and the dogs 22, 22a have rectangular shape, the dogs being in solid block form and substantially filling the portions of the slot occupied thereby as shown. The dogs 22 and 22a are supported by the hammer member 2l against lateral or wobbling movement during slidable movement of the dogs to clutching and declutching positions and at the time of impact.

Pins or rods 22, 22, one for each impact dos 22. 22a, extend through radial slots 2l, 24 in the solid portion of the hammer member 20 4ai; the upper and lower ends of the cross-slot 2| for guiding the dogs in their radial. inward and outward sliding movements with respect to the axis of the hammer member 2l. The pins or rods 22 continue beyond the hammer member 2l and extend into cam slots 2l, 22 in the upper and lower plates 2l, 22, respectively.

The cam slots 2i are generally arcuate in shape and are positioned diametrically with respect to the hammer member 2l and serve to withdraw the dogs or impact members 22, 22a positively back into the cross-slot 2| to free their outer projections 22, 2l, which have substantially equal striking lengths and which are unbroken and continuous throughout their entire lengths. from the path of the anvil jaws 2| as shown in Fig. 6. This occurs following a blow delivering impact of the impact members 22, 22a against the anvil jaws 2| in the operation of the clutch. These cam slots 26 act in the manner shown and described in United States Letters Patent No. 2,425,193, granted August 19, 1947, on an application of Louis P. Fosnot, Serial No. 475,377, filed February l0, 1943, and owned by the'same assignee of this instant application.

The projections 26 are integral with the clutch elements 22, 22a; and are laterally narrower than the body portions thereof so that the body portions need not extend into the openings 20. 22a for the projections to reach and contact the jaws 2|. The opposite side edges of the impact delivering projections 26 are substantially straight and fiat and the impact receiving surfaces 22, 22 of the jaws 2| are complementary thereto.`

The openings 20, 20a in the anvil member Il are substantially equal in size and shape and are oifsetaxially of the anvil member as shown in Figs. l, 3 and 5. This locates one opening below the other to have the upper edge portion 21 of the opening 20 extend slightly below the corresponding edge portion of the opening 22a, and the loweredge portion 22 of the opening 22a extends slightly above the corresponding edge portion of the opening 20 as detailed in Figs. 1, 3 and 5.

The projections 28 of the respective clutch elements 22, 22a have substantially the same length as the width of the openings 20, 20a and are offset in the same manner as said openings so that the projection 26 on one clutch member may enter the opening with which it registers and the same situation applies as to the other projection 26 and its registering opening. When the clutch elements 22, 22a are out of register with the openings, the projections 26 ride against the inner surfaces of the track-ways 21, 22 as provided at the openings 22, 22a and the clutch elements are restrained by said track-ways from entering such openings as shown in Figs. 3 and 4. As the hammer member 22 continues to rotate it brings the clutch elements 22, 22a into register with their individual openings and projections 26 enter said openings to engage the anvil jaws 2| as shown in Fig. 2. If rotation of the anvil member I 2 is arrested or resisted by the tightened nut or bolt the speed of the hammer member 22 under the drive of the tool motor accelerates and causes the clutch elements 22, 22a to strike with powerful rotational hammer blows on the jaws 2| towards which they are driven.

In the specific embodiment of the invention herein shown with a pair of clutch elements 22, 22a carried by the hammer member 20 and an equal number of anvil jaws 2|, the clutch device delivers one hammer blow in each rotative cycle of the hammer member relatively to the anvil member I2. This occurs due to the fact that the mechanism is designed to have the two clutch elements 22, 22a strike their respective anvil jaws 2| simultaneously and the intensity of the hammer blow is increased by allowing the hammer member a free rotative period of approximately 360 degrees for each clutch member to strike its selected law. This will be' apparent from the showing made in Fig. 2. In a diil'erent arrangement than shown in Fig. 2. but embodying the concept of my invention. the clutch elements would operate on selected .iaws on the anvil member and the free period of rotation allowed the hammer member would determine the intensity of the hammer blows as delivered 9!! gli? 941,131 Jaws. Hence, more than one blow atrasos may be permitted per revolution of the hammer member depending on the nature of the clutch design. While one blow to a revolution is permitted by the specific embodiment shown, it is within the contemplation of my invention to control the blows to any rotative cycle desired.

While the pins or rods 33 are herein shown as having a pressed fit within the associated impact members 32. 32a, it is to be understood that a bushing of cushion material may be fitted about each pin within its impact member as shown and described in my co-pending application Serial No. 484,954, now abandoned.

Also, the adapter socket I1 has a shank portion 33, non-circular in cross-section to fit within a similarly shaped bore in the outer end portion of the spindle I5. A suitable spring check arrangement will be employed in the connection to prevent the socket from dropping out of the spindle in handling the tool.

The inner ends of the impact members 32, 32a are provided with recesses 40 to t about the interposed carrier shaft 21 when the impact members move inwardly and provide a stop therefor. The outer ends of the slots 34 provide stops for the outward movement of the clutch elements. The upper plate 25 mounts a bearing unit II for the connection between said plate and the shaft trunnion I0. 1

The operation of the clutch device shown and described is briey as follows: The tool is applied with its socket I1 over the nut or bolt to be driven as shown in Fig. 1. Power is supplied to the tool motor on depressing the valve trigger 3. The reversing valve Il is first set to adjust or determine the direction of rotation of the motor. For setting a nut or bolt with .a right hand thread, the motor is set to rotate in a clockwise direction. On starting the motor, the hammer member 3|) is driven by the drive through the pins or rods 33 and the cam slots 35. In response to this rotation, the impact members 32, 32a are urged outwardly by centrifugal force. As the hammer member 30 is turned with motor relatively to the anvil member I3. the impact members 32, 32a, as soon as they register with their respective openings 20, a will move out into the path of the anvil jaws 2I and engage them. The hammer and the anvil members are now clutched together and the nut or bolt being free to turn is screwed up against the work by the power of the tool. When this occurs the torque of the motor is resisted by the tightened nut or bolt and the further free rotation of the anvil member I6 is arrested. The continued rotation of the plates 25, 28 with the motor causes the cam slots 35 to withdraw the impact members 32, 32a from the path of the anvil jaws 2|.

The tool motor carries the impact members 32. 32a past the freed jaws 2| and opposite the following opening 20a, 20. The track-ways 33. 31 prevent the members from entering these openings and the rotation continues until the next openings 20, 20a are reached whereupon the impact members 32, 32a enter such openings and deliver powerful rotational hammer blows on the relatively stationary jaws. The intensity of such blows is increased by the rotative period afforded the hammer member before striking the next blow. These blows on the jaws 2I further tighten the nut or bolt against the work. The blows of theA members 32, 32a against the jaws 2| imparts a reverse rotation to hammer member 30 which is rotatable relatively to the anvil I3 and the carrier 24. and causes the cam slots 35 to withdraw the impact members 32. 32a' from the path of the anvil jaws as shown in Fig. 6, for repeated blows until the nut or bolt is tightened to the desired tension.

For unscrewlng or removing a tight nut or bolt with a right hand thread the same operations as above described are repeated, except that the rotational hammer blows occur at the start of the action to loosen the nut or bolt and the clutching action occurs when the nut or bolt is loose to be freely unscrewed by the tool motor.

For setting a nut or bolt with a left hand thread the operation first described is performed, except that the reversing valve Il is adjusted to rotate the tool motor in a counter-clockwise direction. And, for removing a nut or bolt with a right'fhand thread the motor is set to rotate in a clockwise direction as first above described with the impact action taking place before the clutching action.

To make the controlled action of the impact members 32, 32a clear, I may point out that in connection with Fig. 2, the impact member 32 registers only with the opening 20, while the impact member 32a registers only with the opening 23a. In Fig. 4, the impact members are shown in their release positions as illustrated in Fig. 3, and it will be noted that the impact member 32a is opposite the opening 20, while the impact member 32 is opposite the opening 20a. In this latter case, the impact members 32, 32a are held out of the openings 20, 20a by the track-portions 31, 33 at the respective openings. Hence, an impact or rotational hammer blow of the clutch device is limited or restricted to one in each complete revolution of the hammer member 33. In short, Fig. 2 shows the blow delivering positions of the clutch.

The advantage gained by my invention is a controlled impact clutch action with an increased intensity of hammer blow with a smaller motor rather than a larger and more powerful motor as would be required to produce the same intensity of blow with the likelihood of twisting ofi` the nut or bolt being set. In the structure of the Fosnot Patent No. 2,425,793, the impact members are so arranged with reference to the anvil jaws that those members and jaws are clutched and declutched twice every revolution. No means is provided to control or restrainthe impacting engagement between the members and jaws to once every revolution and, consequently, the period oi' acceleration of the impact members between the time engagement with the jaws is broken of! and re-occurs is of a somewhat restricted degree. In the structure of the present application, by incorporating the present control means in combination with positively guided impact means which are also positively held against lateral movement at the time of impact, the impacting engagement occurs only once every revolution, thereby giving the impact elements and hammer member a longer period of acceleration resulting in greater impact force and intensity.

The details of construction and arrangement of parts shown and described may be variously changed and modified without departing -from the spirit and scope of my invention. except as pointed out in the annexed claims.

I claim as my invention:

An impact clutch of the character described comprising relatively rotatable hammer and anvil members, the anvil member having spaced ,uvauas .7 jaws and radially extending openings therebetween on opposite sides thereof, and clutch elements mounted on the hammer member having projecting impact delivering portions movable radially through said openings into and out of the path of the jaws to clutch and declutch the hammer and anvil members and for imparting rotational hammer blows oi equal stress in the relative rotation ci the two members, said clutch projecting portions being of substantially equal lengths and unbroken and continuous throughout their entire lengths and being oiset axially with one projecting portion extending -Iorwardly a greater distance than the other and said other projecting portion extending rearwardly to a greater extent, and said anvil openings having lengths complementary to the lengths of the projecting portions to receive the same when in registry therewith in the rotative operation of the hammer member and being oilset axially to provide a trackway at the extreme rearward edge of oneopening against which the non-registering projecting portion may ride and a trackway at the extreme forward edge of the other opening against which the other non-registering projecting portion may ride to allow only the registering projecting portions to enter their corresponding anvil openings.

WALTER G. MITCHELL.

REFERENCES CITED The following references' are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 1,913,046 Callan June 6, 1933 2,326,347 Forss Aug. 10', 1943 2,343,332 Shan Mar. 7, 1944 2,425,793 Fosnot Aug. 19, 1947 2,439,756 Shad' Apr. 13, 1948 

